There is much confusion about the terms 'GPS' and 'SatNav'.

If you determine 'SatNav' to be a 'GPS' with an electronic map then ok. But some 'GPS' units have maps ... so I'll move them over to be called 'SatNav'? I'm thinking of Garmins GPS map 60Cx that I have .. called a GPS...

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Do you need a GPS .. no. People explored without them. Do you need a map ... no ... people explored without those too. Do you need a camleback? No .. people explored without those too.

But you'll be better off with a good map. And I certainly like my 'SatNav' .. I find it more usefull on the fly than a map. For planing (the next days trip, or consulting others) the paper map is more usefull. If you want to get a 'SatNav' get it well before your trip to get use to it. At least 3 months.

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Garmins etrex models come in various flavors .. some have maps .. others don't. I'd certainly go for one with mapping rather than a simple one. The simple ones only tell you where you are (latitude + longitude) and the time. That makes it easier to find your position on a paper map (if it has some grid reference on it eg latitude/longitude). The mapping ones will tell you that AND place you in the center of their displayed map - thus you already have your position and can zoom in and out to see what is around you. Go play with one in a store. Other benefits of a 'SatNav' .. they can tell you sunrise/set times, phase of the moon, tides...

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Backroads are always a problem. Paper maps don't show them unless they are large scale maps - meaning you'll need lots of maps to cover a country. Same kind of thing with 'SatNav' maps - you need a lots of data to store all the small roads, and the screen becomes too congested when you zoom out .. so they disappear until you zoom in.